#ifndef SPECTRALMESHTOOL_HPP
#define SPECTRALMESHTOOL_HPP

#include "moab/Interface.hpp"  // needs to be here to support inline query_interface
#include "moab/Error.hpp"      // needs to be here to support inline query_interface
#include <vector>

namespace moab
{

/** \class SpectralMeshTool
 * \brief Class with convenience functions for handling spectral mesh
 * Class with convenience functions for handling spectral meshes.  See description of spectral
 * mesh handling in doc/metadata_info.doc and in the MOAB user's guide.
 *
 * There are two primary representations of spectral meshes:
 * a) coarse elements: with SPECTRAL_VERTICES lexicographically-ordered array of fine vertices
 *    on each element, and tags on vertices or on elements (with _LEX suffix)
 * b) fine elements: as linear elements made from fine vertices, with tags on vertices
 *
 */
class SpectralMeshTool
{
  public:
    /** \brief Constructor
     * \param impl MOAB Interface instance
     * \param order Spectral order, defaults to 0
     */
    SpectralMeshTool( Interface* impl, int order = 0 );

    /** \brief Destructor
     */
    ~SpectralMeshTool();

    /** \brief Return tag used to store lexicographically-ordered vertex array
     * NOTE: If creating this tag with this call, this SpectralMeshTool instance must already have
     * a non-zero spectral order value set on it; the size of the spectral vertices tag depends on
     * this order. \param sv_tag Spectral vertices tag \param create_if_missing If true, will create
     * this tag if it doesn't exist already
     */
    Tag spectral_vertices_tag( const bool create_if_missing = false );

    /** \brief Return tag used to store spectral order
     * \param so_tag Spectral order tag
     * \param create_if_missing If true, will create this tag if it doesn't exist already
     */
    Tag spectral_order_tag( const bool create_if_missing = false );

    /** \brief Convert representation from coarse to fine
     * Each element in set, or in interface if set is not input, is converted to fine elements,
     * using vertices in SPECTRAL_VERTICES tagged array \param spectral_set Set containing spectral
     * elements
     */
    ErrorCode convert_to_fine( EntityHandle spectral_set );

    /** \brief Convert representation from fine to coarse
     * Each element in set, or in interface if set is not input, is converted to coarse elements,
     * with fine vertices put into SPECTRAL_VERTICES tagged array.  NOTE: This function assumes that
     * each order^d (fine) elements comprise each coarse element, and are in order of fine elements
     * in each coarse element.  If order is input as 0, looks for a SPECTRAL_ORDER tag on the mesh.
     * \param order Order of the spectral mesh
     * \param spectral_set Set containing spectral elements
     */
    ErrorCode convert_to_coarse( int order = 0, EntityHandle spectral_set = 0 );

    /** \brief Create coarse spectral elements from fine elements pointed to by conn
     * This function creates the coarse elements by taking conn (assumed to be in FE ordering)
     * and picking out the corner vertices to make coarse connectivity, and the other vertices
     * (along with corners) to make SPECTRAL_VERTICES array pointed to by each entity.
     * \param conn Connectivity of fine (linear) elements, in FE ordering
     * \param verts_per_e Vertices per entity
     * \param num_fine_elems Number of fine elements represented by conn
     * \param spectral_set Set to which coarse elements should be added, if any
     * \param start_idx Starting index in conn (for parallel support)
     * \param local_gids If non-null, will insert all fine vertices into this range
     */
    template < class T >
    ErrorCode create_spectral_elems( const T* conn,
                                     int num_fine_elems,
                                     int dim,
                                     Range& output_range,
                                     int start_idx     = 0,
                                     Range* local_gids = NULL );

    /** \brief Set spectral order for this instance
     * \param order Order set on this instance
     */
    void spectral_order( int order )
    {
        spectralOrder   = order;
        spectralOrderp1 = order + 1;
    }

    /** \brief Get spectral order for this instance
     * \return order Order set on this instance
     */
    int spectral_order()
    {
        return spectralOrder;
    }
    /*
      struct ConnMap
      {
        const short a[16];
      };
      */
    static const short int permute_array[];

    static const short int lin_permute_array[];

  private:
    //! the MB instance that this works with
    Interface* mbImpl;

    //! error object for this tool
    Error* mError;

    //! SPECTRAL_VERTICES tag
    Tag svTag;

    //! SPECTRAL_ORDER tag
    Tag soTag;

    //! order of the spectral mesh being accessed
    int spectralOrder;

    //! order of the spectral mesh being accessed plus one
    int spectralOrderp1;
};

inline SpectralMeshTool::SpectralMeshTool( Interface* impl, int order )
    : mbImpl( impl ), svTag( 0 ), soTag( 0 ), spectralOrder( order ), spectralOrderp1( order + 1 )
{
    impl->query_interface( mError );
}

inline SpectralMeshTool::~SpectralMeshTool() {}

}  // namespace moab

#endif
